1. Field of the Invention
This invention relates to processing of semiconductors used to make microelectronic devices and in particular to vacuum valves used in devices for processing such semiconductors.
2. Description of Related Art
Processing chambers are utilized for a variety of processes performed on microelectronic devices such as microelectronic circuits formed on silicon semiconductor substrates. Since these processes may be operated and performed under vacuum, vacuum gate valves are typically employed. Such vacuum gate valves, when used as wafer pass-throughs between vacuum chambers, are often referred to as slit valves. When the slit valve gate is open, semiconductor wafers may be moved from a transfer chamber to a load lock or process chamber or vice-versa. When closed, these valves prevent gas leakage between the transfer chamber and the process chamber. While such slit valves provide generally reliable seals for most processes, certain new deposition and clean processes have been found to rapidly attack elastomeric seal materials utilized in the slit valves. The attack on such elastomeric seal materials typically causes particle contamination or xe2x80x9caddersxe2x80x9d on wafers and also may cause vacuum leakage across the valve itself. Although a wide variety of elastomers are available, none thus far tested have shown a significant improvement in life over the normally employed fluoroelastomers.
The concept of purging the general area with an inert gas has been discussed in Japanese Patent Publication No. 6-185672. In this publication entitled Gate Valve Device For Use With A Vacuum, a guillotine type valve assembly employs gas ducts either in the valve seat or in the valve plate. These gas ducts are used to carry a non-active gas into the gap area between the valve plate and the valve seat. While such an approach has its advantages for shielding the O-rings used in the assembly with an inert gas during processing, the disclosed structure does not provide particularly effective control over the inert gas flow rate or distribution, and an overflow of such inert gas may interfere with the processing of the microelectronic device itself in the chamber.
Accordingly, there is a need for a valve system which may utilize a purge gas more efficiently and in a manner which would not tend to interfere with the processing of the microelectronic device.
Bearing in mind the problems and deficiencies of the prior art, it is therefore an object of the present invention to provide an efficient purge gas system for elastomeric seals in gate or slit valve assemblies used in microelectronic device processing.
It is another object of the present invention to provide a method and system whereby the purge gas is employed more efficiently.
It is a further object of the present invention to provide a method and system in which the purge gas is less likely to interfere with the processing of the microelectronic device in the processing chamber.
The above and other objects, which will be apparent to those skilled in the art, are achieved by the present invention which comprises, in a first aspect, a vacuum valve assembly for use in a vacuum processing chamber comprising: a vacuum processing chamber vacuum valve; a seat defining an opening in the vacuum valve, the seat having a sealing face adjacent to the opening and normal to the direction of the opening; and a gate having a sealing face adapted to mate with the seat sealing face, the gate being movable toward and away from the seat sealing face to seal and open the vacuum valve opening. A continuous elastomeric seal extends around the vacuum valve opening between the gate sealing face and the seat sealing face of sufficient size such that when the gate is positioned to seal the vacuum valve opening, there exists a gap between the gate sealing face and the seat sealing face. A purge gas port system has an inlet for a purge gas, an essentially continuous outlet extending around the vacuum valve opening and adjacent the elastomeric seal and gap, and a manifold system connecting the inlet and the outlet. When a purge gas is introduced through the inlet, the manifold distributes the gas to the outlet which evenly distributes the gas to the vicinity of the continuous elastomeric seal around the vacuum valve opening in the gap between the gate sealing face and the seat sealing face.
The purge gas port system may be disposed in the seat or in the gate. When in the latter, the purge gas port system outlet is preferably defined by a first gate portion having the continuous elastomeric seal secured on the gate sealing face and a second gate portion secured within the first gate portion and facing the vacuum valve opening, so that the purge gas outlet is formed by a gap between the first and second gate portions extending essentially continuously around the first gate portion adjacent the elastomeric seal. The gap between the first and second gate portions forming the purge gas outlet may be smaller than the gap between the gate sealing face and the seat sealing face.
In the vacuum valve assembly, the purge gas outlet may be formed by an opening narrower than the gap between the gate sealing face and the seat sealing face. The purge gas port system outlet itself may be a slit, a series of holes or slots, a porous media adjacent the elastomeric seal, or a porous portion of the elastomeric seal.
In another aspect, the present invention comprises a vacuum processing chamber comprising a vacuum processing chamber having a vacuum valve; a seat defining an opening in the vacuum valve, the seat having a sealing face adjacent the opening and normal to the direction of the opening; and a gate having a sealing face adapted to mate with the seat sealing face. The gate is movable toward and away from the seat sealing face to seal and open the vacuum valve opening, and includes a continuous elastomeric seal on the gate sealing face around the vacuum valve opening of sufficient size such that when the gate is positioned to seal the vacuum valve opening, there exists a gap between the gate sealing face and the seat sealing face. There is also provided a purge gas port system in the gate having an inlet for a purge gas, an essentially continuous outlet in the gate sealing face extending around the vacuum valve opening and within and adjacent the elastomeric seal, and a manifold system connecting the inlet and the outlet. When a purge gas is introduced through the inlet, the manifold distributes the gas to the outlet which evenly distributes the gas to the vicinity of the continuous elastomeric seal around the vacuum valve opening in the gap between the gate sealing face and the seat sealing face.
The purge gas port system outlet may be defined by a first gate portion having the continuous elastomeric seal secured on the gate sealing face and a second gate portion secured within the first gate portion and facing the vacuum valve opening. The purge gas outlet is formed by a gap between the first and second gate portions extending essentially continuously around the first gate portion adjacent the elastomeric seal. The gap between the first and second gate portions forming the purge gas outlet is smaller than the gap between the gate sealing face and the seat sealing face.
In another aspect, the present invention provides a vacuum processing chamber having a vacuum valve; a seat defining an opening in the vacuum valve, the seat having a sealing face adjacent the opening and normal to the direction of the opening; and a gate having a sealing face adapted to mate with the seat sealing face. The gate is movable toward and away from the seat sealing face to seal and open the vacuum valve opening, and includes a continuous elastomeric seal on the gate sealing face around the vacuum valve opening of sufficient size such that when the gate is positioned to seal the vacuum valve opening, there exists a gap between the gate sealing face and the seat sealing face. There is also provided a purge gas port system in the seat having an inlet for a purge gas, an essentially continuous outlet in the seat sealing face extending around the vacuum valve opening and within and adjacent the elastomeric seal, and a manifold system connecting the inlet and the outlet. When a purge gas is introduced through the inlet, the manifold distributes the gas to the outlet which evenly distributes the gas to the vicinity of the continuous elastomeric seal around the vacuum valve opening in the gap between the gate sealing face and the seat sealing face. The gap between the first and second gate portions forming the purge gas outlet may be smaller than the gap between the gate sealing face and the seat sealing face.
A further aspect of the present invention provides a method of extending life to a seal in a vacuum valve used in a vacuum processing chamber. The method comprises providing a semiconductor wafer processing chamber having a vacuum valve seat, a gate closing the vacuum valve seat, and a seal between the gate and the vacuum valve seat, the seal being exposed to the chamber. The method then includes introducing a reactive gas mixture to the chamber to process a semiconductor wafer therein, the reactive gas mixture comprising a reactive gas, adapted to react with a portion of the semiconductor wafer, diluted by a carrier gas, the reactive gas also being reactive with the seal. Thereafter, the method also includes introducing the carrier gas through an essentially continuous opening into the vicinity of the seal between the gate and the vacuum valve seat, with the carrier gas continuously flowing so as to initially shield the seal from the reactive gas and then subsequently pass into the chamber and mix with the reactive gas. The seal may form a gap between opposing sealing faces of the gate and seat, and the carrier gas may be introduced through an essentially continuous opening adjacent to narrower than the gap between the gate and seat sealing faces.
In yet another aspect, the present invention provides a method of extending life to a seal in a vacuum valve used in a vacuum processing chamber comprising providing a microelectronic circuit processing chamber having a vacuum valve seat, a gate closing the vacuum valve seat, and a seal between the gate and the vacuum valve seat, the seal being exposed to the chamber. The method then includes introducing a reactive gas mixture to the chamber to process a microelectronic device therein, the reactive gas mixture comprising a reactive gas adapted to react with a portion of the microelectronic device, diluted by a carrier gas, wherein said reactive gas is also reactive with said seal. The method then includes introducing a portion of the reactive gas, such as oxygen into the vicinity of the seal between the gate and the vacuum valve seat, the reactive gas portion flowing so as to initially shield the seal and then subsequently pass into the chamber and mix with the remaining reactive gas. The carrier gas may also comprise oxygen. The reactive gas portion is preferably introduced through an essentially continuous opening into the vicinity of the seal between the gate and the vacuum valve seat. The seal may form a gap between opposing sealing faces of the gate and seat, so that the reactive gas portion is introduced through an essentially continuous opening in the gate or seat. The reactive gas may include NF3.